command         actual             expected           ok/not ok

du -c           1.47TB used        1.47TB used        ok

zfs list        used 2.48TB        used 1.47TB        not ok
                avail 206GB        avail 1.2TB        not ok

zpool list      size 3.64TB        size 3.64TB        ok
                used 3.31TB        used 1.95TB        not ok
                avail 334GB        avail 1.69TB       not ok

Windows right   Disk size 2.67TB   Disk size 2.67TB   ok
  click disk,   Used 2.47TB        Used 1.47          not ok
  properties    free 206GB         free 1.2TB         not ok

Windows select  total file size    total file size
  all files,      1.48TB             1.48TB           ok
  right click,
  properties

There was a change where snapshots are no longer shown by default.
This can be configured back to the old behaviour setting the zpool
"listsnapshots" property to "on"

Otherwise, you need to use the "-t snapshot" list.

But, a much better method of tracking this down is to use:
    zfs list -o space

That will show the accounting for all dataset objects.
 -- richard

zfs list -t all

zfs list -t snapshot